1. Field of the Invention
This invention relates to lubricating oil additive compositions which provide effective dispersant performance coupled with minimal attack upon fluorohydrocarbon-type engine seals and lubricating oil compositions containing said additive compositions. More particularly, this invention relates to lubricating oil dispersant additive compositions prepared by reacting substituted succinic acid or derivatives thereof with a basic salt of aminoguanidine under selected conditions and lubricating oil compositions containing said dispersant additive compositions.
2. Description of the Prior Art
The presence of water and precursors of sludge in lubricating oils constitutes a very serious problem that is associated with crankcase lubricating oils. There occurs in the lubricating oil various foreign particles, such as dirt, soot, and products of decomposition that result from the breakdown of the lubricating oil. The combination of water and such foreign particles results in the deposition of sludge which has a deleterious effect upon the efficient operation of the engine containing the lubricating oil. In order to prevent the deposition of sludge, various detergents and dispersants are added to the lubricating oil composition.
Today, flexible engine seals comprising fluorohydrocarbon compositions are being used in assembling internal combustion engines. These seals are used to prevent leakage of lubricants at those points where moving parts, such as crankshafts, leave the engine. Of course, any appreciable leak of the lubricant from the internal combustion crankcase is very undesirable. Consequently, an important consideration when selecting the dispersants for use in the lubricating oil composition, in addition to maintaining the cleanliness of the engine, is their compatibility with fluorohydrocarbon crankshaft seals and clutch plate liners in transmissions. These seals comprise fluorohydrocarbon elastomers which are often attacked by the dispersant. For example, Mannich dispersants are incompatible with such fluorohydrocarbon-type engine seals.
In U.S. Pat. No. 4,379,064, Cengel, et al., disclosed the passivating of basically reacting polyamine dispersants to fluorohydrocarbon compositions that are employed in internal combustion engines by the mild oxidation of such polyamine dispersants.
In U.S. Pat. Nos. 3,272,746 and 3,341,542, Le Suer, et al., disclose lubricating oil compositions containing acylated nitrogen compounds prepared, for example, by reacting a substituted succinic acid or derivative thereof with a nitrogen-containing compound, such as ammonia, aliphatic amines, aromatic amines, heterocyclic amines, or carboxylic amines. The resulting detergent composition comprises an oil-soluble, acylated nitrogen composition characterized by the presence within its structure of (A) a substantially hydrocarbon-substituted polar group selected from the class consisting of acyl, acylimidoyl, and acyloxy radicals wherein the substantially hydrocarbon substituent contains a least about 50 aliphatic carbon atoms and (B) a nitrogen-containing group characterized by a nitrogen atom attached directly to said relatively polar group. In Example 38 of these patents, polyisobutene-substituted succinic anhydride, aminoguanidine bicarbonate, and mineral oil were mixed and heated at a temperature of 130.degree. C. (266.degree. F.) to 165.degree. C. (329.degree. F.) for 5 hours. The residue was mixed with mineral oil and heated to 150.degree. C. (302.degree. F.) and filtered. The resulting product was used as a lubricating oil additive and found to be an effective dispersant. These patents teach that the mixture of acid-producing compound and the nitrogen-containing reactant is usually heated at a temperature above about 80.degree. C. (176.degree. F.), preferably within the range of about 100.degree. C. (212.degree. F.) to about 250.degree. C. (482.degree. F.). The patents teach that guanidines are included in sources of nitrogen-containing compounds and present, as examples, guanidine, 1,3-diphenylguanidine, and 1,2,3-tributylguanidine. These patents do not indicate that the resulting product comprises triazoles. Furthermore, there is no suggestion that the dispersants prepared according to the disclosure of these patents would be either deleterious to or compatible with certain types of engine seals, e.g., seals comprising fluorohydrocarbon elastomers. The disclosure is too ambiguous and too broad to teach the present invention.
In U.S. Pat. No. 4,491,527, Lange, et al., disclose ester-heterocycle compositions useful as "lead paint" inhibitors and lubricants, e.g., compositions comprising a major proportion of a pentaerythritol ester of an alkenyl succinic acid in which the alkenyl group contains at least about 30 carbon atoms and a minor proportion of a heterocyclic condensation product of said alkenyl succinic acid derived from a 5-membered ring heterocycle containing at least 2 ring hetero atoms separated by a single carbon atom, at least one of said hetero atoms being nitrogen. The heterocyclic condensation product is characterized by the presence of at least one heterocyclic moiety including a 5- or 6-membered ring which contains at least 2 ring hetero atoms, separated by a single carbon atom. Such ring hetero atoms may be oxygen, sulfur, and nitrogen, with at least one thereof being nitrogen. Most often, the heterocyclic moiety contains a maximum of three hetero atoms and a 5-membered ring, preferably, a triazole or thiadiazole ring, and, most desirably, a 1,2,4-triazole ring. This patent teaches that aminoguanidine and salts of aminoguanidine, such as aminoguanidine bicarbonate, are examples of acyclic heterocycle precursors which may be reacted with the proper acid or acid derivative group. This patent does not suggest that a fluorohydrocarbon-type engine seal would be compatible with such ester-heterocycle composition that is prepared by the method disclosed in this patent.
It has not been found that a lubricating oil dispersant additive composition can be prepared by reacting an alkyl-substituted dicarboxylic acid compound, such as an alkyl-substituted succinic acid or acid anhydride, with a basic salt of aminoguanidine under selected conditions and that the resulting product comprising alkyl bis-3-amino-1,2,4-triazole will perform acceptably as a lubricating oil dispersant and will be compatible with engine seals made of flourohydrocarbon elastomers.